Functional imaging techniques are being used to characterize brain activation patterns in normal subjects and individuals with neurological disorders affecting human communication. Brain activation patterns characterized using PET, fMRI or other brain mapping techniques may be used to characterize phenotypic presentation and neurological consequences of communication disorders. PET scans are performed on the GE Advance and Scanditronix PC2048-15B tomographs using the H215O method. Data are analyzed using Statistical Parametric Mapping software and newer covariance techniques developed in the section. fMRI studies are performed on 1.5 and 3.0 Tesla instruments. Functional images are acquired using spiral, echoplanar imaging and spin-tagging methods. Data are analyzed using MEDx, IDL, and SPM software and newer covariance techniques developed in the Section.PET studies in individuals with developmental stuttering demonstrated hemispheric lateralization patterns that differed from those observed in control subjects, providing a model for the pathophysiology of this disorder (Brain, 120: 761-784, 1997). PET studies in normal subjects during sleep and wakefulness demonstrated unique patterns of cerebral activity associated with each of the individual sleep stages (Brain, 120: 1173-1197, 1997; and Science, 279:91-95, 1998). Functional MRI studies in deaf and hearing individuals demonstrated similar left hemisphere, but distinct right hemisphere, recruitment for English and American Sign Language (PNAS, 95: 922-929, 1998; Neuroreport 9:1537-42, 1998). A number of studies are being prepared for publication: PET studies in normal volunteers demonstrated unique cerebral activation patterns associated with motor and linguistic elements of speech and significant differences for propositional vs. automatic speech. PET studies in persons fluent in both English and American Sign Language (ASL) demonstrated a robust left hemispheric lateralization for both spoken and signed language; intrahemispheric differences were detected however that appeared to reflect both linguistic and motor-expressive differences between English and ASL. PET studies in patients with spasmodic dysphonia demonstrated altered patterns of activity in motor and premotor cortices and basal ganglia that suggest a pathyophysiological model for motor dysfunction in this disorder. PET studies of ASL production in deaf subjects. Functional MRI studies at 1.5 Tesla have revealed unique patterns of cerebral activity associated with text comprehension, discrete phases of verbal working memory and modification of central auditory processing by attention. PET studies of language processing in familial and non-familial left handers, central auditory processing in control subjects and central plasticity in deaf subjects following cochlear implantation are currently underway. fMRI and PET studies in Parkinson's Disease, Tourette's syndrome, and recovery of function in post-stroke aphasia are continuing.